Naked black hole wanders in space

Artist’s conception of how the “nearly naked” supermassive black hole originated. On the left panel, the black hole begins its encounter with another, larger black hole. In the middle panel, the stars are stripped away. On the right, the black hole emerges from the encounter with only the remnants of its galaxy intact. Credit: Bill Saxton, NRAO/AUI/NSF.

Most, if not all, galaxies host a super massive black hole (SMBHs) at their centres. As galaxies wander through space they collide and in most cases their SMBHs end up orbiting each other and eventually they merge. Now, astronomers used the Very Long Baseline Array (VLBA), a radio astronomy instrument made up of 10 identical 25m antennae around the world, to detect a SMBH speeding away from the core of a much larger galaxy with a velocity approximately 2000 Km per second. The SMBH, named B3 1715+425, is located in a cluster of galaxies called ZwCl 8193 and scientists concluded that is the result of a collision between B3 1715+425’s host galaxy and a much larger one, with an even larger black hole. B3 1715+425 is almost naked since it had most of its stars stripped away during the collision and will now continue to travel in space but probably will never escape the cluster of galaxies it belongs. Eventually, in a billion years or so, B3 1715+425 will consume the remaining of the stars and gas that surround it and will become dimmer as it will run out of “fuels”. When this happens the black hole will be only detected through its huge gravity effect.

Astrophysicist had to look at more than 1200 galaxies to come across such a peculiar observation. A question that the discovery raises is how many more black holes like B3 1715+425 exist in the universe. Using the data they get from the VLBA with the synergy from new optical telescopes, like the Large Synoptic Survey Telescope (LSST) scientists hope they will discover more black holes that wander naked in space.